This invention relates to a banded-type implosion protection cathode ray tube reinforced by a band which is applied by shrink fit.
To improve safety of a cathode ray tube against explosion, a reinforcing band is generally applied around the periphery of a face plate constituting a portion of the bulb of the cathode ray tube. Among various methods of applying the reinforcing band may be mentioned shrink fit method. According to this method, an annular reinforcing band 1 shown in FIG. 1 is heat expanded and then applied onto the periphery of the face plate 2a of the bulb 2. Then the reinforcingd band 1 is cooled to room temperature, thus causing it to tightly clamp the face plate with desired clamping force.
However, the periphery of the face plate 2a and the reinforcing band 1 have certain manufacturing error or tolerance so that, in order to smoothly fit the reinforcing band and cause it to manifest the desired clamping force with a small heat expansion thereof, it is necessary to manufacture the outer peripheral length of the face plate and the inner peripheral length of the reinforcing band with highly accurate manufacturing tolerances. Where the relationship between the inner and outer peripheral lengths is not adequate, insufficient clamping force or incapability of applying the reinforcing band would result. The prior art reinforcing band has been manufactured by welding together opposing ends of a metal strip so that the inner peripheral length of a completed annular reinforcing band was not always accurate.
Further, in the prior art banded-type implosion protection cathode ray tube as shown in FIGS. 2A and 2B, a plurality of mounting lugs 3 are provided between the outer periphery of the face plate 2a and the reinforcing band 1. Due to the thickness of the mounting lugs 3, gaps 4 are formed between the face plate and the reinforcing band, thus decreasing the clamping force. Accordingly, in the prior art construction, shims are inserted into the gaps for the purpose of preventing the decrease in the clamping force. However, insertion of thin shims is not only troublesome but also displaces the mounting lugs 3.